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Alternative fuels spark cupola research.

In his paper on alternate fuels for cupola operations, R. Nafziger of the Albany Research Center recalled previous studies that showed that calcined anthracite had been used in some foundries as a successful foundry coke substitute. Later, pilot-scale tests proved that anthracite and bituminous coals could replace UP to 40% of charge coke.

Nafziger said there is new interest in substitutes because of recent coke oven closings due to stringent environmental concerns and safety regulations, the rising cost of new ovens, and the market weakness for coke by product chemicals. If a fraction of the coke could be replaced by fuels of lower rank without sacrificing metal quality, the economics of cupola iron could be improved, coking coals could be conserved and coke shortages could be avoided.

The chemical composition and strength characteristics of iron melted with calcined anthracite are comparable to the same properties of iron melted with conventional cupola fuels, the only concession being the need for higher wind box pressure.

Anthracite coal can replace up to 40% of the charge coke in a pilot-scale plant and up to 10% of cement-bonded coke breeze. Although chopped tires can be used to partially replace up to 20% of charge coke, use would be restricted to units with wet scrubbers. Charcoal briquettes can replace 20% of charge coke; pitch-bonded coal or uncalcined petroleum coke behave similarly at the 20% and 40% replacement levels, respectively, but are unsatisfactory for melting gray iron.

Wood block additions to charge coke proved unsatisfactory because of heavy sparking, and all types of formed fuels or waste products broke down in various unacceptable ways that rendered them undesirable for use in cupolas.

According to a paper presented by S.P. Hay of Hickman, Williams & Co., carbon injection into cupola tuyeres has been used for a decade to decrease melting costs by lowering foundry coke usage, to control carbon and to increase the melt rate. in addition to these three benefits, the process has a favorable effect on silicon, carbon and manganese recoveries.

Using statistical process control (SPC), Hay was able to evaluate data to track changes in the coke and charge makeup and in the critical raw materials that influence the carbon, silicon and manganese levels in the iron. His hypothesis was that he was able to reduce the amount of foundry coke in the charge and replace it with injected carbon while realizing higher carbon levels in the iron. Higher silicon and manganese recoveries produced further economic benefits to the injection system. Using the carbon injection system, it was also possible to alter the carbon levels of the iron much faster than by conventional charge adjustment methods.
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Title Annotation:95th AFS Casting Congress, May 5-9, 1991 - Birmingham, Alabama; A Technical Review: Melting Methods & Materials Division
Publication:Modern Casting
Date:Jun 1, 1991
Words:442
Previous Article:'Help the eagles fly.' (95th AFS Casting Congress, May 5-9, 1991 - Hoyt Memorial Lecture)
Next Article:"Close enough" no longer good enough.
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